Propylene alkylation



May 30, 1961 w. s. KNoBLE ETAL 2,986,590

PROPYLENE ALKYLATION Filed June 30, 1959 2,986,590 Patented May 30, 1961 ice 2,986,590 PROPYLENE ALKYLATION Filed June 30, 1959, Ser. No. 823,944 4 Claims. (Cl. 260683.59)

McGovern, Beaumont, by mesne assignments, to Socony Mobil Inc., New York, NX., a corporation This invention has to do paraffin by reaction liquid acid catalyst.

More specifically, it has to do with the alkylation of propylene and isobutane in the presence of liquid sulphuric acid.

The process of alkylation for the production of isoparatlinic compounds of high anti-knock capability and boiling with the gasoline boiling range is well known. To a great extent, the process has been practiced with the object of effecting the combination of isobutane and butylene to form isooctane. Since other olefins, such as Propylene and amylene will also enter into such reactions with a resulting fuel ingredient of good capability, and since such olefins are commonly present in the euent streams of many refinery operations, there is a wide practice of alkylating these olefins, either in streams relatively concentrated as to the specific oleiins or as a mixture of oleflns of C3 to C5 range.

One of the major disadvantages heretofore existing with the operation of alkylation of a feed stream high in propylene content has been a high consumption of acid per unit of alkylate produced, and, frequently, an end boiling point (ASTM) of alkylate product which was unduly high.

This invention has for its principal object the provision of an alkylation process capable of handling feeds having a very high percentage of propylene with a low acid consumption to produce an alkylate of high octane number and an acceptable end boiling point.

The process of this invention is best carried out in a system wherein the reaction ingredients are subjected to a vigorous mechanical agitation, such as an alkylation reaction system employing the well-known Stratco Contactor, of the Stratford Engineering Company, and for purposes of illustration, a diagrammatic showing of such a system is aixed hereto.

Referring to the drawing, 1 is a reactor, to which acid is introduced by pipe 2, and fresh feed by pipe 3. The reaction mix is subjected to mixture and caused to flow by impeller 4, driven by motor means 5. The reactor is provided with an internal shell 6, and cooling coils 7. The reaction mixture is forced to flow by the impeller 4, first through the annular space between the reactor wall and the inner shell 6, and then around the cooling coils 7, and a portion is continuously withdrawn by pipe 8 to settler 9, where it is separated into an upper hydrocarbon phase and a lower acid phase. Of the acid withdrawn from the settler through pipe 10, a portion goes through pipe 11 to the next reactor (a normally operating setup comprises several groups of reactors and settlers) and the remainder passes through pipe 12 to return to the reactor, being joined on its way by fresh acid introduced through pipe 13. The hydrocarbon phase from the top of settler 9 passes through pipe 14 to the cooling coils 7 in reactor 1 and thence through pipe 15 to suction trap 16. Cooling is effected by partial evaporation of the hydrocarbon in this cycle, with evaporated material with the alkylation of an isowith an olen in the presence of a being withdrawn to compression. through pipe' 17 and cold liquid returning through pipe 18 to join the material in pipe 14 in passage through coils 7. Reactor eiiuent hydrocarbon is withdrawn through pipe 19, and passes to distillation, there to be separated into. product and appropriate fractions forV return to the reaction.

In a particular operating set-up comprisingrS reactorsettler groups operated in parallel onvhydrocarbon feeds and in series with respect to acid, i.e., fresh acid to #1, and settler acid phase passing downward through the reactor series, attempts to alkylate a feed whose olefin content was 100% propylene indicated an extremely high acid consumption.

An operation conducted for over 6 months had the following characteristics:

Table I Operating conditions (average):

Propylene in olens, vol. percent 60 Isobutane to olefin ratio, voL/vol 10.5:1 Reactor temperature, F 50 Acid in reactor emulsion, vol. percent 56 Strength fresh acid, wt. percent H2SO4 98.5 Strength spent acid, wt. percent H2504- 90.5 Impeller r.p.m S10-540 Tests on debutanized total alkylate (average):

distillation point, F 320 End distillation point, F 428 Octanenumber, F-l clear 89.1 Octane number, F1|3 cc. TEL 101.4 Acid consumption #t acid: Per gallon debutanized total alkylate 1.85

AttemptstoY alkylate olefin mixtures containing more than 65-70% propylene (the remainder is butylene) resulted in debutanized total alkylate end points above 440 F. and octane number (F-1-l-3 cc. TEL) below 100.5, with acid consumption of the order of 2# and higher per gallon of alkylate. The external isobutane to olefin ratio could be varied from 8:1 to, 15:1, and the reactor temperature from 40 to-65 F. without signicant change. The variable which gave significant change was the propylene content of feed, and as that went up it was accompanied by a rise in acid consumption and a lessened quality of alkylate.

An increase in impeller r.p.m., other conditions being relatively constant, was also found to be without significant effect.

It was found that if the impeller speed was raised, and at the same time the amount of acid recycled to the reactor was raised, signicant changes did occur. One physical change was quickly apparent, namely, the appearance of an extensive emulsion layer in the acid settler 9, a condition which it was previously ltaught should be avoided.

Typical changes in operating conditions and results are shown below:

Table II Operating conditions:

Propylenes in oleiins, vol. percent 65 Isobutane to olefin ratio, VOL/vol. 10.5 :1 Reactor temperature, F. 45 Acid in reactor emulsion, vol. percent 6.5 Strength fresh acid, wt. percent H2804 98.5 Strength spent acid, wt. percent H2804 90 Impeller r.p.m. 620 Tests on debutanized total alkylate:

90% distillation point, F. 273 End distillation point, F. 383 Octane number, F-l clear 91.8

Octane number, F-1-l-3 cc. TEL 102.9 Acid consumption acid: Per gallon debutanized total alkylate 0.7

With such operation, major changes upward in the propylene content of the feed may be made without substantial increase in acid consumption and without substantial product degradation, as shown by the following:

Table III Operating conditions:

Propylene in olefins, vol. percent 85-90 Isobutane to olen ratio, vol./vol. 9:1 Reactor temperature, F. 45-50 Acid in reactor emulsion, vol. percent 65 Strength fresh acid, wt. percent H2504 98 Strength spent acid, wt. percent HZSO@g 90 Impeller r.p.m. 620 Tests on debutanized total alkylate:

90% distillation point, F. 287 End distillation point, F. 395 Octane number, F-1 clear 89.0 Octane number, F-l-i-S cc. TEL 101.5

Acid consumption at acid: Per gallon debutanized total alkylate Even when operating upon an olen feed stream composed almost wholly of propylene, the results Aare quite desirable, as shown by:

Table 1V Operating conditions:

total alkylate 1 1 The inventive concept herein set forth is that for successful alkylation of an olefin feed consisting largely or wholly of propylene, to get a debutanized total alkylate of high octane number and desirable end point below 400 F., without excessive consumption of acid catalyst, it is necessary to employ a high energy input to the reactor, coupled with a high percentage of acid in the reactor, resulting in a tight emulsion, i.e., a thorough, uniform dispersion of the reactor contents, and a small particle size for the discontinuous phase, which is hydrocarbon.

Desirable conditions for the proper conduct of this operation will of course in some cases vary from those used in the more common alkylation with butylene as the predominant olefin.

The temperature at which this type of alkylation is conducted does not appear to be of great moment as an operating variable. Alkylation of straight propylene has been examined over a temperature range of 45" F. to 75 F. without significant variance in the quality or end point of alkylate product.

Isoparafiin to olefin ratios do not differ in great measure from those already established by experience. The external iso/olefin ratios may be varied over the range from 8/1 to 15/1 without significant differences in amount or nature of debutanized total alkylate produced with high propylene feed. For the operations herein-described, the internal ratio of isobutane to propylene is of more factual significance. The actual internal ratio utilized with best success is of the order of 400 units (volume) of isobutane to one unit (volume) of olefin. Experience indicates that from about 65% propylene in total olefin to 100% propylene, this ratio can be relatively constant with successful operation. It is indicated that 4 the external ratio should not be below about 8/1, which, under the conditions described, is about a 400/1 internal ratio.

The amount of acid in the reactor is an important variable. Expressed in terms of percent of reactor volurne, it should not be below about 55%, preferably of the order of 60 to 65%. Expressed in terms of volume of acid into the reactor per unit volume of olen, it should be at least 13/1, although with proportions of propylene in total olen ranging upward from 65% it does not appear necessary to increase the above noted volume ratio of acid to olen.

The amount of energy utilized is another variable of importance. What is really desired is an emulsion, uniform in nature, tight in character, that is, slow to break or resolve into two phases, in which the hydrocarbon disperse phase is in uniform and small particles. While the existence or lack of such an emulsion can be readily recognized, the statement of how to achieve it apparently can be made only in terms of energy input to the reactor contents in proportion to the olen charge. Experience indicates that the minimum energy input to the liquid content of the reactor is of the order of 0.2 horsepower per gallon per hour of olefin. Note that this figure is the energy input to the liquid and not the energy expended in that turbine or motor which drives the irnpeller.

Acid strength becomes a minor variable in a system with multiple units, each consisting of a reactor and settler, through which the acid catalyst passes in series, becoming slightly weaker in each unit. To secure best operation, acid should be so handled in such a system that in the last reactor of a series of reactors it is not below H2504. And in such a system, it may be found desirable to vary the acid recirculation, or, in other terms, the lpercent of reactor volume occupied by acid or volume of total acid to reactor per volume of olen charge, with the strength of the acid. Experience indicates that in a system using 98.5% strength fresh acid and spending to 90% acid, the acid volume in the first reactor of a series could be of the order of 65 to 70%, and in the last reactor 55 to 60% of reactor volume.

Under the conditions thus outlined, it has been found that olefin streams containing from about 65% propylene up to propylene can be successfully alkylated to produce a debutanized total alkylate having an octane number (F-l) clear of the order of 90, a leaded octane number (F-l plus 3 cc. TEL) of the order of 102, and an end point below 400 F., and to accomplish this with the consumption of from about 0.5 pound of acid to about 1.2 pounds of acid per gallon of debutanized total alkylate.

We claim:

l. That method for the sulphuric acid catalyzed alkylation of an isoparafn with an olefin feed containing in excess of 65 volume percent of propylene to produce a debutanized total alkylate having an octane number (F-l) clear, of the order of 90, a leaded octane number (F-l-l-B cc. TEL) of the order of 102 and an end distillation point (ASTM), below 400 F., while experiencing an acid consumption not greater than about one pound of acid per gallon of debutanized total alkylate which comprises: continuously feeding to an alkylating reactor a fresh olefin feed containing in excess of 65 volume percent of propylene, an isoparaftin stream sufcient to maintain within the reactor an isoparaftin/oleiin ratio of about 400/ 1, a mixture of incoming acid and recycled acid sufiieient to maintain within said reactor acid to the extent of at least about 55 percent of its volume, applying to the liquid mixture in said reactor mixing energy amounting to not less than about 0.2 horsepower per gallon of olen fed per hour, withdrawing an efiluent stream from said reactor, separating said effluent stream into a hydrocarbon phase for removal from the system, and an acid phase, a substantial portion of which acid phase is recirculated to said reactor.

2. That method for the sulphuric acid catalyzed alkylation of an isoparatl'in with an olen feed containing from about 65 Volume percent to 100 volume percent of propylene to produce a debutanized total alkylate having an octane number (F-l), clear, of the order of 90, a leaded octane number (F-1+3 cc. TEL), of the order of 102 and an end distillation point (ASTM), below 400 F., while experiencing an acid consumption of from about 0.5 to about 1.2 pounds of acid per gallon of debutanized total alkylate which comprises: continuously feeding to an alkylating reactor a fresh olefin feed containing from about 65 volume percent to 100 volume percent of propylene, an isoparatin stream suicient to maintain within the reactor an isoparan/olen ratio of about 40G/'1, a mixture of incoming acid and recycled acid suiiicient to maintain within the reactor acid to the extent of at least about 55 percent of its volume, applying to the liquid mixture in said reactor mixing energy amounting to not less than about 0.2 horsepower per gallon of oleiin fed per hour, withdrawing an effluent stream from said reactor, separating said effluent stream into a hydrocarbon phase for removal from the system, and an acid phase, a substantial portion of which acid phase is recirculated to said reactor.

3. That method for the sulphuric acid catalyzed alkylation of an isobutane with an olen feed containing in excess of 65 volume percent of propylene to produce a debutanized total alkylate having an octane number (F- 1), clear, of the order of 90, a leaded octane number (F- 1|3 cc. TEL) of the order of 102 and an end distillation point (ASTM), below 400 F., while experiencing an acid consumption not greater than about one pound of acid per gallon of debutanized total alkylate which comprises: continuously feeding to an alkylating reactor a fresh olein feed containing in excess of 65 volume percent of propylene, an isobutane stream sufficient to maintain within the reactor an isoparain/olen ratio of about 400/ 1, a mixture of incoming acid and recycled acid sufcient to maintain within said reactor acid to the extent of about 55 percent of its volume, applying to the liquid mixture in said reactor mixing energy amounting to not less than about 0.2 horsepower per gallon of olen fed per hour, withdrawing an eluent stream from said reactor, separating said etl'luent stream into a hydrocarbon phase for removal from the system, and an acid phase, a substantial portion of which acid phase is recirculated to said reactor.

4. That method for the sulphulic acid catalyzed alkylation of an isobutane with an olen feed containing from about 65 Volume percent to 100 volume percent of propylene to produce a debutanized total alkylate having an octane number (F-l), clear, of the order of 90, a leaded octane number (F-1-l-3 cc. TEL), of the order of 102 and an end distillation point (ASTM), below 400 F., while experiencing an acid consumption of from about 0.5 to about 1.2 pounds of acid per gallon of debutanized total alkylate which comprises: continuously feeding to an alkylating reactor a fresh oleiin feed containing from about 65 volume percent to 100 volume 'percent of propylene, an isobutane stream sucient to maintain within the reactor an isoparalin/olen ratio of about 400/ 1, a mixture of incoming acid and recycled acid sucient to maintain within the reactor acid to the extent of at least about 55 percent of its volume, applying to the liquid mixture in said reactor mixing energy amounting to not less than about 0,2 horsepower per gallon of olen fed per hour, withdrawing an eluent stream from said reactor, separating said effluent stream into a hydrocarbon phase for removal from the system, and an acid phase, a substantial portion of which acid phase is Irecirculated to said reactor.

References Cited in the tile of this patent UNITED STATES PATENTS 

1. THAT METHOD FOR THE SULPHURIC ACID CATALYZED ALKYLATION OF AN ISOPARAFFIN WITH AN OLEFIN FEED CONTAINING IN EXCESS OF 65 VOLUME PERCENT OF PROPYLENE TO PRODUCE A DEBUTANIZED TOTAL ALKYLATE HAVING AN OCTANE NUMBER (F-1) CLEAR, OF THE ORDER OF 90, A LEADED OCTANE NUMBER (F-1+3 CC. TEL) OF THE ORDER OF 102 AND AN END DISTILLATION POINT (ASTM), BELOW 400*F., WHILE EXPERIENCING AN ACID CONSUMPTION NOT GREATER THAN ABOUT ONE POUND OF ACID PER GALLON OF DEBUTANIZED TOTAL ALKYLATE WHICH COMPRISES: CONTINUOUSLY FEEDING TO AN ALKYLATING REACTOR A FRESH OLEFIN FEED CONTAINING IN EXCESS OF 65 VOLUME PERCENT OF PROPYLENE, AN ISOPARAFFIN STREAM SUFFICIENT TO MAINTAIN WITHIN THE REACTOR AN ISOPARAFFIN/OLEFIN RATIO OF ABOUT 400/1, A MIXTURE OF INCOMING ACID AND RECYCLED ACID SUFFICIENT TO MAINTAIN WITHIN SAID REACTOR ACID TO THE EXTENT OF AT LEAST ABOUT 55 PERCENT OF ITS VOLUME, APPLYING TO THE LIQUID MIXTURE IN SAID REACTOR MIXING ENERGY AMOUNTING TO NOT LESS THAN ABOUT 092 HORSEPOWER PER GALLON OF OLEFIN FED PER HOUR, WITHDRAWING AN EFFLUENT STREAM FROM SAID REACTOR, SEPARATING SAID EFFLUENT STREAM INTO A HYDROCARBON PHASE FOR REMOVAL FROM THE SYSTEM, AND AN ACID PHASE, A SUBSTANTIAL PORTION OF WHICH ACID PHASE IS RECIRCULATED TO SAID REACTOR. 